how to find the max and min value of x and y axis at specified intensity?

I have a image containing white and black pixel i need to find the maximum and minimum value of x and y axis at specified intensity(white intensity). or you can say that i need to find the center of which contains white color????

Answer 1

[Image Analyst]

That's exactly what I do in my Image Segmentation Tutorial. I find the centroid and bounding box of all bright objects. Just what you want to do. See http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862